Insulation composition for electrical devices



R. P. LUTZ 2,496,948 INSULATION COMPOSITION FOR ELECTRICAL DEVICES Feb. 7, 1950' Filed Dec. 27, 1945 /AIM? A770 i only to Patented Feb. 7, 1950 v 1 2,496,948 PATENT orrice i INSULATION COMPOSITION FOR ELECTRICAL DEVICES Raymond P. Lutz,

ern Electric Company,

oak Park, 111., assignor to Westlncorporated, New York,

N. Y., a corporation of New York Application December 27,1945, Serial No. 637,431

4 Claims.

This invention relates to the insulation of electrical devices and moreparticularly to an insulating composition and method for applying the composition to an electrical device.

An important problem in themanufacture of electrical apparatus is the application thereto of electrical insulation. The insulation serves not electrically insulate electrical conductors and other members from one anothenbut serves likewise to protect the apparatus from the undesirable effects of weather and moisture or water in particular. It is a well known phenomenon that insulations applied to electrical members when dry function satisfactorily but when exposed to moisture absorb it gradually and lose their resistance properties. In many cases the insulating requirements for electrical members specify that immersion in water should have no significant adverse efiects upon the operation thereof. Electrical members such as coils, transformers, motors, capacitors and similar devices are frequently located in exposed conditions where they may be subject to rainfall, inundation by water, various corrosive atmospheres,

metallic dusts, and the like. It is particularly desirable that the insulation applied to the apparatus should protect the conductors under these adverse conditions whereby normal functioning of the apparatus is maintained.

It has heretofore been proposed to encapsulate. an electrical device in an outer shell of a resin ous material and to flll the interior of the shell with a fluid penetrating resinous material, both the inner and outer insulating materials being heat treated to thermoset or cure the materials.

One difiiculty heretofore encountered was the fact that the resinous materials employed had poor wetting properties for the insulation of the elecdevice, tending to leave voids and incom- Another diftrical pletely filled spaces or interstices.

, flculty encountered was the fact that unpolymerized resinous materials are somewhat acid and would therefore attack the device being insulated if the time required for polymerization was too long.

The object of the present invention is to pro- I vide a thermosetting resinous material having good wetting properties for the insulation of electrical devices.

A further object isto provide a method of aptaken in conjunction with the accompanying drawing, in which Fig. 1 is an elevational view partly insection showing an electrical device in the process of treatment;

Fig. 2 is a similar view illustrating a further step in the process;

Fig. 3 is a similar view illustrating a still further step in the process, and

Fig. 4 is an elevational view of a completely insulated electrical device.

The process ofencapsulation and filling comprises essentially the steps as illustrated in Figs. 1 to 3 of applying an initial cup-like shell of a relatively thick resinous material to the exterior of the member being insulated as shown in Fig.1.

The electrical device shown in Fig. l as illustrating the invention comprises a core of magnetic material ll provided with a coil [2. The device is immersed in relatively thick resinous material to such a depth as to leave a small open area at the upper end of the coil. This immersion will cause an open ended shell I3 of the material to be applied on the device as indicated by the dot and dash lines (Fig. 1). The device is then transferred to a heating oven to polymerize the resinous material in the shell l3. Thereafter it is immersed in a fluid penetrating solventless type of resin composition as illustrated in Fig. 2, the shell l3 serving'to hold the penetrating resin in the device. The device is then again transferred to a baking oven to polymerize the fluid resinous material, after which the outer shell is completed as illustrated in Fig. 3 by dipping the open end of the device in a relatively thick resinous material. Upon polymerization of this thick enclosing layer the device is completed as shown in Fig. 4.

In the preferred embodiment of the invention in carrying out the process of encapsulation, two distinct types of resinous insulating materials may be employed. In order to provide the outer shell about an electrical device a relatively thick resinous material having thixotropic 40 properties is desirable. The relatively thick resvinous material should be capable of bridging small gaps in the insulation without penetrating far into the interior of the coil or the like. Generally the thick resinous material carries a filler composedof finelydivided inorganic solid ma- 7 terial in order to enable the building up of a relatively thick outer protective coating which may be from 5 mils to or more in thickness. A tool-thick coating compared to the size of the member obviously may be subject to cracking due to thermal expansion of the various elements of the encased member and may lack a certain degree of required flexibility. In the case of relatively large members such, for example, as large generator coils, such exterior coating of thick resin may be reinforced by means of tapes of inorganic fibrous material to provide for adequate mechanical characteristics.

One composition that may be used in practicing the invention is a resin composed of ,100 60 parts by weight'of castor oil and 30 parts by weight of maleic anhydride heated for several residue produced by steaming pine wood chips hours to'rproduce'afcastor oil=maieate whichis itoremovevvolatile substances therefrom: extractthen disso vedineo pa s by weieh of mo ome ic ingthe steamed wood chi s'wlth a'coal' tar hydro- S y e plus .02% of hydroquinone o i h p carbon, evaporating the coal tar hydrocarbon and ma u e po er a on. T is ma eri l s om other volatile constituents of the extract from W p W i pr per ies for -insulation and t theextracttoproduce a solid residue, extracting has th efore the fieet of being p d y e -rosinr from said residue with a light petroleum insulation. It has been found tha h addition hydrocarbon, and separating the extract from the f /2% 0f Vinsol increases the WBt tiIIgD light gpetroleum "hydrocarbon insoluble comof the material so that it willeifectivelypenetram lpnt Ofthejrjgiflfil extra ti n of pine wood the insula i a ria a d pa e therebetween- 'tofacilitate thecoating of said insulation with Vinsol is a hard dark-"coloredxresinous:ma- .ssaidematerial. terial co p s a gasoline-insoluble D Q 2. .A coating composition for coating insular in p c y eXtraCting r i o WOOdWitii tionpf an electrical device consisting of a solua c al a hyd r n' y vap rati t ac n tion of from '15 to 95 parts by weight of styrene the re wi h a petroleum hyd o rb n it wirith'from 5 "to 25 parts by 'wei'ght "of: the ester moving the solvent and recovering the'gasoline- "reacti n pro'duct'ofmastor oil and"malelc-.acid 1 "insoluble resin *as described i'in Patent No. t w lg x te 5%;;by 2, issued March 1940' t0 LuCiilSU'HaH- weight of analcohol-soluble resin which isthe When this material is USEd'YOI the "outer shell residue prbducedzby'steaming pine wood'chips to pulverized c is d d h e oee the "remove volatile .substances thereirom, -"extractt X r l C p op rt s Of he So ution and-"1% of "ing the steamed wood chips-with a coal tarhydroiibenze'yl DerOXide "Catalyst is "added, based carbon; evaporating the coal tar hydrocarbonzand the weight'of'the resin components. other volatile' constituents of *theextract from Another composition 'which' may be luse'd is 'azs the-extract'to produce -.a solid residue; extracting e n Co po d of 6 p yweight of linseed rosin from said residue with a light petroleum oil', 15.8 parts of castor oil 'and'23.2 parts 'of maleic hydrocarbon, and separating the extract from the anhydride =mixed togetherat a'temperature of li'ght petroleum hydrocarbon--. insoluble com- 175 to 200 C. and '75 p s f this resin ponents of the original extraction'of pine wood S d" 'p cy e to increase the wetting properties of the solution. of'hydroquinone"is added-as'aninhibitor'of'pre- '-3. A coating compositionforcoatinginsulamature Polymerization arid by Weight of tion' of an-electricaldevice comprising-"aisolution "benzoyl' peroxide catalyst is added. When used of from 30 to 95' parts by weight of'styrene with 'as the outer coating pulverized-mica added 'to from 5't0 70 parts by weight of the ester reaction "thecomposition. Thea'dditionof 5% Vinsolfi*"product'-of"maleic :a'cid=and"castor oil to -which 'to'this material'increases its wetting properties has been added-approximately 15%" by weight'of as described in connection' with" the "first illusan alcohol-soluble resinwhich is *the'residue pro tration-given. duced by' steaming "pine 'wood chips to remove Another material that" maybe effectively'used volatile -substances therefrom, extracting the "is a" solution of styrene :with the ester'reaction-"40'"steamed wood-chips with'a coal tar hydrocarbon, products of ma1eicacid=andca5t0r oil described =evaporatingthe coal tar-hy'drooarbon and other in thecopending applicationof swiss-et'aln-serial volatile constituents of -the extractfrom theex- -'No. 527,483, filed March'21, 1944,'nowU. S.'-Patent "tractto' pro'duce-a'solid' residueyextracting rosin "23393953. 'To this composition is added from said residue-with a light ,petroleumxhydro- 'of Vinsol to increase its wetting properties and-Separating the extract h li "When these materials are used'as the "fluid im- "petroleum -hydr s u l Components o =pregnating-arid penetrating materialsfor'thecoil the or nal ex a t on f pin 'w d p v within the shell, the fillers such as mica "are SW P p t somitted. 4. A" coating composition 'for coating insulat been found t t t atalysts usedvgo tion of an electrical device comprising'a thermothe acceleration of" polymerization of resinous Setting eopolymer 0f ii e y- "materials such as the benzoyl-peroxide deteriorate "rene and PP y'- y W g tef an a100- after being added to the resinous "compositions, hol-soluble'resin which is the residue produced by *thereby increasing the length of time during steaming pine wood-chips to removevolatile subwhich the materials remainunpolymerized and extracting the S e med-wood resulting in' an attack of the slightly =acid unchips wi h ae al yd a n vap rat n polymerized'materials on the-electrical device. the v(30841 tar y on and other volatile con- This diiiiculty may be overcome byadding ad- *stituentsof the extract' from the extract to pro- -ditiona1 catalysbfrom 1311119 to time to maintain duce=asolid; residue, extracting rosin 'from Said the'optimum reaction time. *In the treatment 0 residue With a light Petroleum y c bo and of transformer coils .l2% to 25% "of catalyst "separating-the extract from the-light petroleum 'was added to the treating baths for every s-hours r carb nsolub e mp n ts f th ri inal that the bath was maintainedfor thedippingopextractionOfpmewooi eration, resulting in the avoidancepf" an objec- RAYMOND itionable attack or the unpolymerized-resinous material on thecoils. j "REFEBENCES'IJITED What isv claimed is: f "jThe'following. references. areof. record'in'the 1. A coating compositionffor"coating"'insula- "file of this patent:

.'tion.;of an electrical device comprising a'thermo Y setting 3 copolymer of 301to' 95 partsiby weight UNITED STATES PATENTS .of'styreneandfi to704partsby weightotan "Number :Name I Date alkyd resin consistingeof, a;halfrester"of.castor 2,193,026 H311 a 4 :oil and maleic acid .towhichfisgadded approxiv2,416,133 Berberich .4 Feb. 1891947 amately ..5%. by Weight. ofia. wettingwagent ,con- 2,4 3,87 Clipper Jil1y 15, i947 :sisting -of .analcohbl-soluble. resin .whi'ch'ris .ithet'u' 

1. A COATING COMPOSITION FOR COATING INSULATION OF AN ELECTRICAL DEVICE COMPRISING A THERMOSETTING COPOLYMER OF 30 TO 95 PARTS BY WEIGHT OF STYRENE AND 5 TO 70 PARTS BY WEIGHT OF AN ALKYD RESIN CONSISTING OF A HALF ESTER OF CASTOR OIL AND MALEIC ACID TO WHICH IS ADDED APPROXIMATELY .5% BY WEIGHT OF A WETTING AGENT CONSISTING OF AN ALCOHOL-SOLUBLE RESIN WHICH IS THE RESIDUE PRODUCED BY STEAMING PINE WOOD CHIPS TO REMOVE VOLATILE SUBSTANCES THEREFROM, EXTRACTING THE STEAMED WOOD CHIPS WITH A COAL TAR HYDROCARBON, EVAPORATING THE COAL TAR HYDROCARBON AND OTHER VOLATILE CONSTITUENTS OF THE EXTRACT FROM THE EXTRACT TO PRODUCE A SOLID RESIDUE, EXTRACTING ROSIN FROM SAID RESIDUE WITH A LIGHT PETROLEUM HYDROCARBON, AND SEPARATING THE EXTRACT FROM THE LIGHT PETROLEUM HYDROCARBON -INSOLUBLE COMPONENTS OF THE ORIGINAL EXTRACTION OF PINE WOOD TO FACILITATE THE COATING OF SAID INSULATION WITH SAID MATERIAL. 